Re: How to super harden papers?

Hi Rich,
        I got all my information out of " Photographic Emulsions for
Idiots"
The doubt if the info would be wrong!..
John
----- Original Message -----
From: "Richard Knoppow" <dickburk@ix.netcom.com>
To: <alt-photo-process-l@skyway.usask.ca>
Sent: Saturday, March 26, 2005 2:54 PM
Subject: Re: How to super harden papers?

>
> ----- Original Message -----
> From: "John Cremati" <johnjohnc@core.com>
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Saturday, March 26, 2005 3:59 AM
> Subject: Re: How to super harden papers?
>
>
> > Hi Sandy,
> > Just some thoughts.
> > I know with my little experience in extreme high
> > relief , the ph
> > is said to be the critical factor in the amount of
> > swelling the gelatin is
> > able to do.....The maximum swelling is achieved about a PH
> > of 8.4 with the
> > minimum swelling taking place at about 4.7....... As a
> > thought, maybe you
> > are coating or attempting to size the paper at or close
> > to a maximum
> > condition in the wet state...... Then when dried, it has
> > not sized the paper
> > sufficiently .....
> > Possibility the paper reacts with the gelatin
> > causing the ph to be
> > changed at surface level and again when dry, it does not
> > have the amount
> > of gelatin size necessary to do its job.................
> > Another thought is the pigmented emulsion at a ph
> > of 8.7 causing
> > high relief in the wet state but low relief when
> > dried.....Maybe as a
> > experiment I would try coating the paper using a PH
> > emulsion opposite of
> > what you are using to see what you may see .
> > Please let me know of your progress.
> >
> > John Cremati
> >
> Are you sure that maximum swelling occurs at pH 8.4? It
> seems to me that swelling continues to increase on either
> side of the isoelectric point of the gelatin. Also, pH 4.7
> seems to me rather too low for photographic gelatin as found
> in printing paper although it might be right for the gelatin
> used to make carbon tissue.
>
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@ix.netcom.com
>
>
>
>
> _____________________________________________________
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Received on Sat Mar 26 15:16:14 2005